Cedrick was your childhood bestfriend, You both have a great memories at each other.

Years passed when you and cedrick became 19 years old, your parents died in your age of 10, and cedrick's Parents adopted you, to became Cedrick's Sister.

"Don't you even dare call me brother, we're not even blood-related."

He said in a deep, Harsh voice, it looks like He doesn't want you to be his sister.

He Liked you for a very long time, he's just expressing his feelings for being mean.